Sept 13 (Reuters) - Biogen Inc and Eisai Co Ltd are abandoning two late-stage trials for their Alzheimer's treatment in a widely anticipated move that comes months after the companies scrapped trials of another drug for the memory-robbing disease.

The companies said on Friday the decision was based on the results of a review conducted by a data safety monitoring board, which recommended discontinuing the trials as benefits from the treatment, elenbecestat, did not outweigh its risks.

Shares of Biogen were up 2.3% at $237.60 as some analysts said ending the trial would save the company costs associated with running it through its completion.

"This was widely expected by the investment community, including ourselves, and amounts to a further step in the unwinding of Biogen's expensive, painful and ultimately fruitless investment in Alzheimer's disease drug development," SVB Leerink analyst Geoffrey Porges said.

The companies in March ended two late-stage trials of another experimental Alzheimer's drug, aducanumab.

Aducanumab's failure wiped out more than $18 billion of Biogen's market value, as investors were betting on the treatment to buoy the drugmaker, which is mired in patent issues over its big-selling multiple sclerosis drug Tecfidera and possible competition to spinal muscular atrophy drug Spinraza.

Elenbecestat belongs to a class of drugs called beta amyloid cleaving enzyme (BACE) inhibitors, which act by inhibiting the production of amyloid beta - a protein believed to be a major cause of Alzheimer's disease.

However, drugmakers such as Amgen Inc and Novartis AG, Eli Lilly and Co and AstraZeneca Plc have all abandoned some of their BACE inhibitor trials earlier.

While there may have been similar failures in other companies, as a percentage of one large company's value and its total R&D investment, it would be hard to find a bigger disappointment, Porges said.

Biogen and Eisai said on Friday their latest decision does not impact their other Alzheimer's study testing experimental treatment, BAN2401, which belongs to a different drug class. (Reporting by Manojna Maddipatla in Bengaluru Editing by Saumyadeb Chakrabarty and Shinjini Ganguli)